First, remove the seat and side covers from the bike. Unbolt the fender bits from the tail subframe. There are two sections to this undertail fender, a large one which protects the battery box and is shaped like the tire, and the rear bit which also serves as a mounting point for the turn signals/license plate.

If you want, you can remove that part as well and replace it with a bracket from www.ninjacustoms.biz which will hold your plates and some short stalk signals. It looks clean.

Next, you want to measure the length and width of the space you just created by removing the fender bit(s). I’m not exactly sure what size it was, but make sure you ensure that it’s not too wide or long, as there are a few obstructions. The space is NOT a perfect rectangle. 2.5 to 3 inches is the depth you can use, the shallower, the better, as the rear wheel does travel quite a bit.

Now you need to buy your supplies. I used metal flashing from home depot for 10 dollars, it comes in a roll. It’s just flimsy sheet metal really. You also need tin snips (5.00) a drill with a bit big enough for your rivets, and a pop rivet gun (5.00 as well). Note that I buy my tools at dollar stores and stuff so they’re cheap.

Next, you just need to lay out a design on the flashing, (I’ve attached a basic picture), cut it out, and drill holes for the rivets. Just fold the metal using some kind of straight edge to ensure a good bend and rivet the holes, and you should have a sturdy box. The excess holes are for zip ties, which hold the box to the tail subframe.

I attached a basic plan for the trunk. Just lay the outside edge of this shape out on your flashing and the other lines indicate bends. The little square bits are tabs that hold the box together. They can be the full two and a half inches, but the edges are sharp and it was a little better with small tabs. The box is just as sturdy that way. Use your head as far as symmetry, It should be completely symmetrical, the holes need to line up etc. The measurements are ESTIMATED, measure it yourself to make sure.

Remember to tape up sharp edges, as there are wires in the tail and it would suck if your mod started a fire or something!